Prezi.com

Alternative presentation tool that is interactive.

SCRATCH

http://info.scratch.mit.edu/About_Scratch
Scratch is a programming language that makes it easy to create your own interactive stories, animations, games, music, and art -- and share your creations on the web.
As young people create and share Scratch projects, they learn important mathematical and computational ideas, while also learning to think creatively, reason systematically, and work collaboratively.

A good tool for students to showcase their understanding on Science concepts.

Twiddla.com

Twiddla is an interactive whiteboard which allows users to invite other users to collaborate and doodle on it. It can embed documents and images for user to share with other collaborators.

wordle.com

Wordle is a toy for generating “word clouds” from text that you provide. The clouds give greater prominence to words that appear more frequently in the source text. You can tweak your clouds with different fonts, layouts, and color schemes. The images you create with Wordle are yours to use however you like. You can print them out, or save them to the Wordle gallery to share with your friends.